Passivhaus & Low energy - Energy Efficient To The Core

Commissioned to reduce energy consumption and eradicate local fuel poverty, Callaughtons Ash is a £2million housing development for South Shropshire Housing Association using timber frame and a Passivhaus approach.

Sat in Much Wenlock's green landscape, the 820sq m development comprises one, two and three-bedroom homes, including two shared ownership and ten social rentals. Each is designed to offer affordable, environmentally sustainable accommodation. To meet the South Shropshire Housing Association's (SSHA) need for a sustainable solution
to develop low-energy housing stock, Lowfield Timber Frames worked with Architype, to develop a timber system for Callaughtons Ash that minimises energy impact and facilitates maximum airtightness.

Lowfield Timber Frames designed, manufactured and installed a Larsen Truss timber system for the development to reduce build time and maintenance costs while maximising quality and environmental benefits. The building palette of healthy and ecological timber materials forms a sustainable system for long-term efficiency that meets Passivhaus standards. The main objective was to meet the overall aim to develop sustainability and quality while eradicating fuel poverty and improving residents' health and wellbeing in the most cost-effective way.

Callaughtons Ash is an exemplary Passivhaus residential scheme that minimises energy consumption and costs, providing affordable homes in Shropshire. As the most stringent energy standard in the world, Passivhaus certification secures economic, environmental and social sustainability. The Callaughtons Ash scheme was officially certified shortly after the build was completed, guaranteeing ultimate performance and certifying that there are no gaps between predicted and actual results – reassuring residents. The fully bespoke timber system, applies a fabric first approach that requires minimal energy and enables comfortable lifestyles for residents while minimising operational costs to below £100 per annum for average housing types, which is in line with the housing association's core value – affordable, low-energy accommodation.

As TRADA and STA Assure Gold Members, Lowfield Timber Frames implement high-level quality standards, following the Site Safe Scheme to ensure safe, sustainable construction. The timber frame and thermally modified hardwood cladding designed for this project promote the housing association's aim for carbon reduction and a cohesive, circular economy in Shropshire. Lightweight trusses were tacked onto the sheathing to ease the insulation process. The slim, compressed timber web minimises thermal bridging, facilitating reduced heating costs to expand residents' budgets for living costs and other family expenses. 

The Larsen Truss system offered an economic route to achieving impressive U-values of 0.117 W/m2K for the walls  and 0.061 W/m2K for the roof, while also providing support for the cladding system. The compressed timber web reduces thermal bridging, leading to minimised heating costs for residents, who can expect to spend just £70-£100 on energy per annum.

No bolt-on technologies were used, with the exception of the mechanical ventilation and heat recovery (MVHR), which was used as part of the Passivhaus design approach. The aim was to reduce energy consumption as much as possible through highlevel design, insulation, triple glazing, airtightness, mechanical ventilation, heat recovery, considered orientation and window sizes to maximise solar gain and minimise overheating risks. These factors were calculated through the Passivhaus Planning Package (PHPP) to create accommodation that requires virtually zero energy. The building fabric performs well enough not to require bolt-on technologies, which are too often used to offset poor building performance.

By adhering to requirements stipulated by SSHA's community-led building consultancy, Marches Community Land Trust Services and the Much Wenlock Community Plan, construction methods were enforced to manufacture a lowenergy timber system that meets the client brief.

The business rationale for the socially responsible housing association was to end fuel poverty by providing accommodation with excellent thermal properties to achieve a low energy aspiration. The housing association collaborated with the local community to recognise housing needs, concluding that affordability cannot be sacrificed in the build of high-quality, energy efficient homes. It became apparent that there is a need for accessible shared ownership home prices. David Turner, Shropshire Councillor for the Much Wenlock Division said: "It was clear from the consultations that there was a strong need for affordable housing for local people. The homes will, for the first time in Much Wenlock, provide affordable homes for people with a local connection."

Transport and recycling processes were also carefully selected to further minimise carbon footprint. The timber was sourced locally where possible, and waste was avoided as all leftover timber was recycled or used in the biomass plant to produce electricity. 

As it is challenging for new families to afford homes in Shropshire, the scheme offers a new solution to overcome lack of social housing, implementing Passivhaus standards to prioritise residents, the environment and the local economy. Passivhaus certification guarantees that homes perform as predicted at the design stage, maintaining minimal operational carbon.

The Callaughtons Ash development makes shared ownership more affordable and accessible to young people and first-time buyers. This project proves that the combination of a sustainable approach and local skills/materials does not limit design innovation, even when restricted by budget. This is an excellent example of collaboration between a local authority, developer and specialist contractor and this scheme could evolve design standards in social housing to improve quality and wellbeing long-term.

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